In accordance with the present invention, cellulose base fibers, wood for example, are intertwined with and bonded to carrier fibers, and blended with a thermosetting ingredient to create a moldable fibrous mat. The intertwining is done through use of special non-woven web machinery. The bonding is done through either heating of a thermoplastic bonding agent or activation of a chemical bonding agent. The mat is made in the first stage of a two-stage process of making a permanently rigid end product. The thermosetting ingredient, which remains uncured in the first stage, cures under the heat and pressure of the second stage in which the end product is completed.
Prior art in compressed wood fiber technology includes fiberboard, particle board and hardboard, terms applied to a variety of products made primarily from wood fibers, wood chips or shavings. These are not substantially formable. Extreme shapes, similar to those attainable through this invention, can be achieved by a so-called wet slurry process in which wood fibers are mixed with water and other chemicals and formed into a slurry which is applied over a pattern having desired form. While satisfactory products can be made by the wet slurry process, it is a relatively expensive process not only in terms of the amount of energy required but also because of its long manufacturing cycle time and the cost of cleaning the resulting effluent prior to dumping. This invention, however, relates to a dry process and product made therefrom.
It has also been known to form wood fiber based products by dry processing, but these previously known dry processes are capable of producing products having only relatively flat simple shapes and require a minimum of two steps to mold, as opposed to one for this invention.
It is a primary object of this invention to provide a unique dry process of forming a flexible mat consisting essentially of base and carrier fibers, the base fiber being a cellulose fiber, and the carrier fiber being a linking fiber adapted to intertwine or interlock with the base fibers, plus a stage 1 bonding means and a thermoset resin. Suitable base fibers are made of materials such, for example, as wood, jute, sisal, cotton, coconut, kapok, paper, and other cellulose fibers. Products having far more severe draft angles, deeper cavities, and more complex curves can be made from the material produced by this new dry process than could possibly be made by previously known dry processes. Material made by the method of this invention can be molded in one step relatively fast and inexpensively into a variety of items such, for example, as decorative trim panels, automotive headliners, door panels, instrument panels, center trim pillars, package trays, consoles, furniture, luggage, building materials, packaging and the like. Such a product may have areas of differing density to provide portions that are soft to the touch or to provide visual embossing, and to provide both thermal and acoustical insulation. The ability to mold a self-supporting product with areas of low density eliminates the need for separate foam pads to be attached, thus offering significant economies.
A further object is to provide relatively flat, flexible, moldable fiber mat in continuous sheet or in sections which can be handled without damage either manually or by automation, and from which end products can be molded; also to provide a method of making the mat into a final product and the end product itself.
In accordance with a specific embodiment of the invention, the mat may comprise a mixture of wood fibers, thermoplastic carrier fibers that mechanically intertwine with the wood fibers and are also bonded or adhered to them to form interlocking connections which resist separation, and a thermoset resin. The mat fibers are adhered together by heating the mat to a temperature and for a period of time such that the thermoplastic carrier fibers soften and become sufficiently tacky to heat-seal to the wood fibers and to each other, but still substantially retain their essentially fibrous form. The carrier fibers add substantial tensile strength to the mat so that even when products molded therefrom have complicated or difficult shapes and include sharp bends and cut-outs, the body of the mat will, nevertheless, hold together without ripping or tearing when the mold parts close. The thermoset resin will cure and set during a subsequent molding operation, imparting permanent shape, thickness and density to the product. Other materials may be added to the formulation of the mat depending upon the characteristics desired in the finished product.
These and other objects and features of the invention will become more apparent as the following description proceeds, especially when considered with the accompanying drawings.